1. Field
The present invention generally relates to the field of touchless user interfaces, and more particularly, to input pointing devices.
2. Introduction
Motion sensing systems can detect movement of an object. As one example, a radar unit can transmit and receive high energy signals for detecting a large metallic object. High energy signals can reflect of the metallic object due to the properties of the metal. As another example, a weather radar can be used to track storm movement. The radar can determine the storm distance by measuring a time difference between when a radar signal was emitted and when a reflection of the radar signal was received. Estimating a time of flight generally involves detecting a time of arrival of the reflected signal which can be based on detection of a pulse. The quality of the reflected signal can be distorted due to transmission effects or environmental effects.
Radar is commonly used for long range distance measurements, such as tracking a vehicle or tracking a storm. Radar units are generally large devices deployed in broad areas where long distances are common. The time length of a radar pulse is generally small relative to a time distance of the detected object. Pulse compression can enhance the performance of radar range detection. Pulse compression, also known as pulse coding, is a signal processing technique to maximize the sensitivity and resolution of radar systems. Transmitting longer pulses can improve the radar's sensitivity by increasing the average transmitted power. However, lengthening the radar pulse has the effect of degrading the range resolution of the radar because the radio pulse is spread over a larger distance.
Moreover, radar units, or radio frequency signals, are not generally suitable for small and precise range measurements on non-metallic objects. The time length of the pulse can lead to range measurement errors over very short distances. Slight perturbations of a pulse signal can lead to inaccuracies in the time of flight measurement. The pulse can be smeared in time as a result of transmission and reflections which distorts the time arrival for detection. Moreover, sensing devices responsible for emitting and transmitting the pulse signal can be imbalanced. The imbalances produce variations in the pulse that can result to false detections. This can also lead to inaccurate time estimates. Amplitude variations can also lead to detection errors which lead to inaccurate arrival times.